History of Hindu Mathematics: A Source Book v2.c17.s2.t1.24

which means x₁ (= 9) + x₂ (= 7) = 16; x₂ (= 7) + x₃ (= 10) = 17; x₃ (= 10) + x₄ (= 8) = 18; x₄ (= 8) + x₅ (= 11) = 19; x₅ (= 11) + x₁ (= 9) = 20.